Low-range low-power non-line-of-sight (NLOS) indoor localization can enable a host of location-aware Internet-of-Things (IoT) applications. Indoor navigation of public safety officials inside a building is a primary example. The localization tag built in wearable devices would significantly enhance the effectiveness of emergency evacuation, search and rescue operations. Intelligent warehouses and factories can be realized by tracking accurate locations of pallets, equipment robots and people in real-time to eliminate potential safety hazards while maximizing logistics efficiency. In hospitals, tracking of equipment, patients, and personnel can identify and eliminate infectious vectors, addressing a major health care issue. Ubiquitous localization-ready wireless tags to enable real-time tracking and logging of medical personnel/equipment interaction with patients is envisioned.
A mobile tag for everyday IoT applications must be small, low power, low cost, and rapidly deployable without heavy infrastructure investment. This disclosure targets a stringent power budget of <100 μW in average (duty-cycled) and <<100 μW peak power to fully integrate the solution in a centimeter-scale wearable tag. The localization accuracy requirement for a wide class of IoT applications is in the decimeter (10 cm) order and it must be functional in large (up to 100 m per dimension) indoor environments where NLOS scenarios are dominant with multipath-rich RF propagation. To date, there are few existing solutions that adequately address this set of challenging specifications which is critical to a wide set of localization based applications. Low-cost global positioning system (GPS) receivers, for example, cannot establish enough SNR to achieve better than several meters accuracy in indoor settings. WiFi or Bluetooth based indoor localization solutions are available today but their operating range is quite limited (<20 m) and their accuracy is in the order of a few meters that is insufficient to satisfy stringent public safety localization application requirements.
This disclosure introduces a new approach in RF localization that utilizes a frequency-shifting active reflector on a node that echoes the orthogonal frequency division multiplexing (OFDM) ranging signal generated from an anchor. A frequency conversion based full duplex approach enhances the localization range and accuracy beyond the level achievable by conventional narrowband RF localization systems.
This section provides background information related to the present disclosure which is not necessarily prior art.